1. Field of the Invention
This invention relates generally to vasoocclusive devices, and more particularly concerns a vasoocclusive device that has a first elongated, reduced friction configuration in which the vasoocclusive device may be deployed through a catheter or cannula to an anatomical cavity at a site in the vasculature to be treated, and that has a three dimensional second configuration assumed by the vasoocclusive device at the site to be treated for filling the anatomical cavity.
2. Description of Related Art
The art and science of interventional therapy and surgery has continually progressed towards treatment of internal defects and diseases by use of ever smaller incisions or access through the vasculature or body openings in order to reduce the trauma to tissue surrounding the treatment site. One important aspect of such treatments involves the use of catheters to place therapeutic devices at a treatment site by access through the vasculature. Examples of such procedures include transluminal angioplasty, placement of stents to reinforce the walls of a blood vessel or the like and the use of vasoocclusion devices to treat defects in the vasculature. There is a constant drive by those practicing in the art to develop new and more capable systems for such applications. When coupled with developments in biological treatment capabilities, there is an expanding need for technologies that enhance the performance of interventional therapeutic devices and systems.
One specific field of interventional therapy that has been able to advantageously use recent developments in technology is the treatment of neurovascular defects. More specifically, as smaller and more capable structures and materials have been developed, treatment of vascular defects in the human brain which were previously untreatable or represented unacceptable risks via conventional surgery have become amenable to treatment. One type of non-surgical therapy that has become advantageous for the treatment of defects in the neurovasculature has been the placement by way of a catheter of vasoocclusive devices in a damaged portion of a vein or artery.
Vasoocclusion devices are therapeutic devices that are placed within the vasculature of the human body, typically via a catheter, either to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus or to form such an embolus within an aneurysm stemming from the vessel. The vasoocclusive devices can take a variety of configurations, and are generally formed of one or more elements that are larger in the deployed configuration than when they are within the delivery catheter prior to placement. One widely used vasoocclusive device is a helical wire coil having a deployed configuration which may be dimensioned to engage the walls of the vessels.
The delivery of such vasoocclusive devices can be accomplished by a variety of means, including via a catheter in which the device is pushed through the catheter by a pusher to deploy the device. The vasoocclusive devices, which can have a primary shape of a coil of wire that is then formed into a more complex secondary shape, can be produced in such a way that they will pass through the lumen of a catheter in a linear shape and take on a complex shape as originally formed after being deployed into the area of interest, such as an aneurysm. A variety of detachment mechanisms to release the device from a pusher have been developed and are known in the art.
For treatment of areas of the small diameter vasculature such as a small artery or vein in the brain, for example, and for treatment of aneurysms and the like, micro-coils formed of very small diameter wire are used in order to restrict, reinforce, or to occlude such small diameter areas of the vasculature. A variety of materials have been suggested for use in such micro-coils, including nickel-titanium alloys, copper, stainless steel, platinum, tungsten, various plastics or the like, each of which offers certain benefits in various applications. Nickel-titanium alloys are particularly advantageous for the fabrication of such micro coils, in that they can have super-elastic or shape memory properties, and thus can be manufactured to easily fit into a linear portion of a catheter, but attain their originally formed, more complex shape when deployed.
One conventional vasoocclusive coil is known, for example, that has a three dimensional in-filling coil configuration, formed by winding a wire into a helix, and then winding the helix into a secondary form which forms a generally spherical shape, by winding the primary coil about poles placed on winding mandrel. The secondary wound coil is then annealed on the winding mandrel, and the coil is then removed from the winding mandrel and loaded into a carrier for introduction into a delivery catheter. Another similar type of vasoocclusive device is known that can be formed from one or more strands, and can be wound to form a generally spherical or ovoid shape when released and relaxed at the site to be treated. Another implantable vasoocclusive device having multiple secondary layers of primary windings has a final shape that is a generally spherical coil formed of linear or helical primary coils that are wound into a secondary form having three layers. The inner winding is wound and then the second layer formed by winding in the opposite direction of the first layer. The final configuration is a chunky or stepped shape approximately a sphere, ovoid, or egg. Yet another conventional implant for vessel occlusion is made from helical elements of metal or synthetic material by twisting or coiling the elements and forming them into a secondary shape such as a rosette or double rosette for implantation using a catheter, and another vasoocclusive device is known that has a final conical shape. However, due to the tendency of such three dimensional shaped coils to transform into their expanded, final forms when introduced into a catheter in the body, they are inherently more difficult than a helical coil or a straight wire or micro-cable to push through such a catheter for delivery to a site in vasculature to be treated, due to friction between the coil and the catheter through which it is delivered to the site to be treated, which can even result in misalignment of the coil within the catheter during delivery.
There thus remains a need for a vasoocclusive device that has a three dimensional final form that can be used to fill an anatomical cavity at a site in the vasculature to be treated, reduces friction between the coil and the catheter through which it is delivered to the site to be treated, and ultimately helps to prevent coil misalignment. The present invention meets these and other needs.
Briefly, and in general terms, the present invention provides for an improved vasoocclusive coil, that has a three dimensional box or cube-shaped portion, and a method of making the coil. The three dimensional portion will form a basket for filling the anatomical cavity at the site in the vasculature to be treated. The three dimensional portion of the vasoocclusive coil comprises at least one strand of a flexible material formed to have an a first inoperable, substantially linear configuration for insertion into and through a catheter or cannula to a desired portion of the vasculature to be treated, and a second operable, three dimensional box or cube-shaped configuration for occluding the desired portion of the vasculature to be treated. This substantially linear configuration allows for reduction of friction of the coil within a catheter or cannula being used to deliver the vasoocclusive coil to the site in the vasculature to be treated, and ultimately helps prevent coil realignment or misalignment. The ultimate coil volume that otherwise might be limited due to frictional constraints of three dimensional coils will not be compromised with the device of the present invention. The vasoocclusive coil may optionally also include a portion having a first inoperable, substantially linear configuration for insertion into and through a catheter or cannula to a desired portion of the vasculature to be treated, and a second operable configuration that is substantially J-shaped or helically shaped, for filling and reinforcing the three dimensional box or cube-shaped basket portion, for occluding the desired portion of the vasculature to be treated, in order to combine the best qualities of a three dimensional coil and a J-shaped or helical coil.
The present invention accordingly provides for a vasoocclusive device that is adapted to be inserted into a portion of a vasculature for occluding the portion of the vasculature for use in interventional therapy and vascular surgery. The vasoocclusive device comprises at least one strand of a flexible material formed to have a first inoperable, substantially linear configuration for insertion into and through a catheter or cannula to a desired portion of the vasculature to be treated, and a second operable, three dimensional configuration for occluding the desired portion of the vasculature to be treated. The vasoocclusive device advantageously has a portion having a second operable, three dimensional box or cube shape for filling the anatomical cavity at the site in the vasculature to be treated, and may optionally include a portion having a second operable, substantially J-shape or helical shape for filling and reinforcing the distal, three dimensional box or cube shaped portion when it is implanted at the site in the vasculature to be treated.
The present invention also provides for a method of making the vasoocclusive device. The method generally comprises the steps of winding at least one strand of a flexible shape memory material about a mandrel formed of a refractory material in a three dimensional configuration of the vasoocclusive coil to form a distal portion of the vasoocclusive coil; heating the at least one strand of a flexible shape memory material wound about the mandrel for a sufficient period of time to impart the form to the shape memory material included in the device to form an operable, three dimensional configuration of the vasoocclusive coil; removing the vasoocclusive coil from the mandrel; and cold working the vasoocclusive coil into a desired elongated configuration for placement into a catheter or cannula for use. In one presently preferred embodiment, the mandrel about which the at least one flexible strand forming the vasoocclusive coil is wound has a substantially orthogonal or cubical body with a plurality of posts disposed on the body. In a preferred aspect, six posts are disposed on the body aligned with the three orthogonal x, y and z axes through the body of the mandrel, for aligning and shaping the box or cube shaped portion of the vasoocclusive device as it is wound on the mandrel. In one presently preferred embodiment, one of the posts is provided with a handle that can optionally also be used as a mandrel for winding a portion of the vasoocclusive coil with a helical shape. In another preferred aspect of the method, the step of heating comprises heating the at least one strand of a flexible shape memory material wound about the mandrel at a temperature of about 1100xc2x0 F. for at least about 4 hours to impart the form to the shape memory material included in the device to form an operable, three dimensional configuration of the distal portion of the vasoocclusive coil.